VOS3000 DTMF Modes Configuration Complete Guide Important

VOS3000 DTMF Modes Configuration Complete Guide Important

Table of ContentsVOS3000 DTMF Modes Configuration Complete Guide ImportantWhat are VOS3000 DTMF Modes? VOS3000 DTMF Transmission Methods (VOS3000 DTMF Modes) SIP INFO Mode RFC2833 Mode INBAND Mode DTMF Configuration Location DTMF Configuration Parameters (VOS3000 DTMF Modes) DTMF Receive Setting RFC2833 Specific Settings DTMF Send Settings DTMF Mode Conversion (VOS3000 DTMF Modes) IVR DTMF Analysis Parameters DTMF Troubleshooting Common DTMF Issues DTMF Troubleshooting Steps Important DTMF Notes (VOS3000 DTMF Modes) FAQ – VOS3000 DTMF Modes Related Resources Need Call Center Setup Support?

What are VOS3000 DTMF Modes?

VOS3000 DTMF (Dual-Tone Multi-Frequency) modes define how touch-tone signals are transmitted during VoIP calls. DTMF signals are essential for IVR navigation, voicemail access, calling card services, and any application requiring user input during a call. VOS3000 supports three primary DTMF transmission methods: SIP INFO, RFC2833, and INBAND, each with distinct characteristics and use cases.

Proper DTMF configuration ensures seamless interaction between different VoIP systems and devices. Understanding DTMF modes is essential for troubleshooting, as we cover in our VOS3000 troubleshooting guide.

VOS3000 DTMF Transmission Methods (VOS3000 DTMF Modes)

SIP INFO Mode

SIP INFO transmits DTMF signals as separate SIP messages within the signaling channel. Each key press generates an INFO message containing the digit information.

Works without media proxy

Simple implementation

May not be supported by all devices

Timing issues with rapid key presses

RFC2833 Mode

RFC2833 (now RFC4733) transmits DTMF as special RTP packets within the media stream. This is identified in SDP as a=rtpmap:101 telephone-event/8000.

Industry standard method

Best timing accuracy

Works well with media proxy

Requires RTP stream to be active

INBAND Mode

INBAND DTMF encodes tones directly into the audio stream as actual sound frequencies. The receiving end must decode these audio tones.

Works with any codec

No special protocol support needed

Can be distorted by low-bitrate codecs (G729)

Difficult to detect accurately

DTMF Configuration Location

Configure DTMF settings in VOS3000 at:

Gateway > Additional Settings > Protocol > DTMF

Phone > Additional Settings > Protocol > DTMF

For understanding protocol settings, see our guide on SIP trunking configuration.

DTMF Configuration Parameters (VOS3000 DTMF Modes)

DTMF Receive Setting

OptionDescriptionAllAccept all DTMF types. Once a type is received, only that type is accepted for the call (recommended)SIP INFOOnly accept SIP INFO DTMFRFC2833Only accept RFC2833 DTMFINBANDOnly accept INBAND DTMF

Best Practice: Set DTMF Receive to “All” to maximize compatibility. The system will automatically detect and lock to the first DTMF type received during a call, preventing duplicate detection.

RFC2833 Specific Settings

ParameterDescriptionPayloadThe payload type value in RTP for RFC2833 DTMF (default: 101). Must match the SDP negotiation.Use Peer RFC2833 AbilityWhen checked, RFC2833 capability is determined by peer’s SDP. If unchecked, VOS3000 always declares RFC2833 support.

DTMF Send Settings

ParameterProtocolDescriptionDTMF SendH323Auto (recommended), RFC2833, or other modesDTMF SendSIPAuto (recommended), RFC2833, SIP INFO, or INBAND

For related protocol configuration, see our callee rewrite rule guide.

DTMF Mode Conversion (VOS3000 DTMF Modes)

VOS3000 can convert between DTMF modes when media proxy is enabled:

Received ModeConfigured Send ModeActionRFC2833SIP INFOConvert RFC2833 to SIP INFOSIP INFORFC2833Convert SIP INFO to RFC2833RFC2833/SIP INFOINBANDDiscard original and send as INBANDINBANDRFC2833/SIP INFOPass through INBAND + send converted signal

DTMF Configuration Issues?

Our experts can help resolve DTMF compatibility problems between different VoIP systems.

WhatsApp: +8801911119966

IVR DTMF Analysis Parameters

For IVR services that require DTMF input, additional parameters control DTMF detection:

ParameterDefaultDescriptionIVR_ENABLE_PARSE_INBANDOffEnable INBAND DTMF analysisIVR_ENABLE_PARSE_SECOND_INBANDOffEnable second line INBAND DTMF analysisIVR_PARSE_DTMF_MODEAutoDTMF analysis mode

DTMF Troubleshooting

Common DTMF Issues

DTMF not detected: Check if DTMF mode matches between endpoints

Duplicate digits: Set DTMF Receive to “All” to prevent double detection

Missing digits: Verify payload type matches in SDP negotiation

Delayed response: Check network latency and jitter buffer settings

DTMF Troubleshooting Steps

Verify both endpoints support the same DTMF mode

Check SDP negotiation for RFC2833 payload type

Enable signaling trace to capture DTMF messages

Test with different DTMF modes if issues persist

For comprehensive troubleshooting, see our guide on VOS3000 one-way audio troubleshooting.

Important DTMF Notes (VOS3000 DTMF Modes)

Critical Notes:

When VOS3000 receives both SIP INFO and RFC2833 from the same endpoint, only the first detected DTMF type is processed

If INBAND is received and RFC2833/SIP INFO is configured for sending, VOS3000 passes through INBAND and sends converted signal

With media proxy enabled, VOS3000 terminates the received RFC2833 and re-sends according to configured DTMF settings

Without media proxy, RFC2833 messages are passed through transparently

FAQ – VOS3000 DTMF Modes

Q1: Which DTMF mode should I use?

A: RFC2833 is recommended for most deployments as it’s the industry standard. Set DTMF Receive to “All” and DTMF Send to “Auto” for maximum compatibility.

Q2: Why is DTMF not working with G729 codec?

A: INBAND DTMF can be distorted by low-bitrate codecs like G729. Use RFC2833 or SIP INFO instead, or enable media proxy for DTMF conversion.

Q3: What is the default RFC2833 payload type?

A: The default payload type is 101, but this must match the SDP negotiation between endpoints. VOS3000 can automatically adapt to different payload values.

Q4: Can DTMF work without media proxy?

A: Yes, SIP INFO and RFC2833 work without media proxy. INBAND always works without media proxy since it’s part of the audio stream.

Q5: How do I test DTMF functionality?

A: Call an IVR system or voicemail and press keys. If the system responds correctly, DTMF is working. Use signaling trace to debug issues.

Related Resources

VOS3000 Official Downloads

VOS3000 2.1.4.0 Manual

VOS3000 Call Testing Guide

Elastix PBX Configuration

Professional VOS3000 Support

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Need Call Center Setup Support?

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